A method is provided for polymerizing an olefin monomer in a reactor with a highly active polyolefin polymerization catalyst system. The method includes introducing a catalyst system comprising a catalyst and a catalyst activator into the reactor containing the olefin monomer with less than 10 seconds or no pre-contacting time of the catalyst and the catalyst activator prior to introducing the catalyst and the catalyst activator into the reactor. The catalyst system may have a standard adjusted catalyst activity of greater than 10 gPgcat−1hr−1.